Flower power

Blooming Phyllo 

This morning, Vlaya, Xavier and I carefully made a paper template for where to bore holes in the PCV disc to attach the Phyllo shell. Vlaya had previously finished placing threaded inserts on a 3D-printed sculpture. We then went to the school mechanic, Mr Croullebois, to bore the holes and attach the sculpture. 

The threaded inserts we used have a screw thread diameter of 3.5, which it turns out is not standard in France. Thankfully, the school go-to guy for electronics, Karim Ben-Kalaia, who by luck was visiting Mr Croullebois at that time, offered to take a look in his own workshop and promptly returned with a handful of suitable screws 🙂 

Without further ado, here’s what it look like : 

Just a quick note : the motor currently in the fixed base has been damaged during our tests and makes a pretty annoying creaking noise while turning.… Read more

UART’s breakthrough !

Today, thanks to Xavier’s tips, I finally managed to write a satisfying workflow for the UART server. I used the ChibiOS’ mailbox system on the STM32 and emulated it with queues on the ESP32.

Each applications is in charge of allocating the actual memory space of the data. The server only manages a 256 words long table to store a single pointer for each of the 256 possible ports. This pointer references two mailboxes. One enables the application to provide a buffer and its length to the server while the other enables the server to signal that a given buffer has been filled with a given number of bytes.… Read more

Phyllos Galore

One has holes in it, one was printed in the wrong material (phosphorescent ), one got too small after our acetone smoothing test, one got warped due to wrong temperature settings… and the last one seems just fine, but might potentially explode in a thousand pieces when we’ll try to spin it at 30 RPS 🙂

We would like to thank the Zortrax M200 who spent 120 hours in total printing these, hopefully it will get some rest one day (not today though, we still need to print a bunch of supports )

Improving the 3D PCB supports

I talked in this post about the 3D supports I’m making in order to easily fit the 62 petal PCBs and 12 processor PCBs in the Phyllo. Since then, I’ve made quite a few changes and progress on the 3D design:

Here you can see both the phyllo, the support for the processor PCBs (blue) and for the petal PCBs (red), and the PCBs (green)

The cylindric pieces are here in order to have thickness around the holes in which I will put the threaded inserts.

I tried to print the processor PCB support, but it failed because of wrong settings, here is the result of the second print:

It’s not perfect yet, there is one spot where the structure got shifted, but it’s still a very promising result.… Read more

Random GDB behavior

We just got a new dev board: a Nucleo144 STM32H743ZI. We will use it for all the code which will run on the STM32H743VIT6 processor of the main board.

Before anything else, does anyone know why I keep getting “Program received signal SIGTRAP, Trace/breakpoint trap 0xfffffffe in ?? ()” half of the time after I flash a simple “hello world” program on the STM32H743 and execute it on gdb (using continue) ? The other half of the time it works just fine.

Anyway, back to the article. After carefully memorizing all of the 3289 pages of the reference manual (as would any good ROSE student do), I started coding the module which will send SPI frames to the processor PCBs (see the Software Architecture post).… Read more

Tuning up

Motor update

Since yesterday, Sibille and I have worked on reducing the voltage threshold for motor acceleration we’ve mentioned here

After a meeting with Alexis yesterday and with the school mechanic this morning, we have two main leads.

Reflashing BLHeli ESC

The first lead is to take a look and the programmable  parameters of the ESC. We previously hadn’t given this much thought, but ESCs usually allow for the tweaking of several parameters in how they control the motor. Usually there’s a way to access these settings by playing with the PWM throttle input and using the feedback bips to identify various menus.… Read more

UART flow control

Today, as I was working on implementing the different servers from my last post, I realized a problem occurring on the UART connection between the main_esp and the main_stm. As I previously discussed in that post, I had to tackle the issue of distributing the traffic on the UART data bus.

To this end, I began to write a sort of server on the ESP32. It copies the port system on an internet server. The first byte of each frame encodes the function the following data line must be transferred to. In this approach, two problems must be tackled.… Read more


As explained in this post, Xavier and I worked on a setup to measure the motor speed. We had to laser-print a drilled plastic plate and some fixation for the dev-board with the optical sensor we’ve borrowed from LitSpin (TCUT1600X01). 


The plastic disk is thin enough to slide between the emitter and the receptors of the optical sensor, and has a small aperture on the edge so that once per rotation the receptors see the emitter and their output goes high.

The optical sensor, which we thought we damaged on Friday, actually works very well. We had some bugs when integrating the dshot code to control the motor’s speed, but very quickly we were able to measure the speed, and to determine the correspondence between a dshot command and an actual speed at a given voltage.… Read more

Mechanical issues and motor troubles

The root of the problem

Yesterday Sibille and I brought the Phyllo structure with the faulty motor (see this post) to the school mechanic, Mr Croullebois. We disassembled the structure, and it turns out the motor shaft goes slightly lower than the motor base, so when we screwed it tight it would scrape against the aluminum plate underneath. 

Mr Croullebois bored a depression in the middle of the plate so we wouldn’t have this problem anymore, and then we reassembled everything with the other motor that we used for tests and knew to be working. The motor that was in the structure spins more freely now, and we managed to make it run, but there is a weird creaking sound from time to time.… Read more


Yesterday, Xavier and I went through the STM32F207 documentation to finish preparing the code for the LED-driving processors. As we explained on Thursday, we would like to go bare-metal on this one.

Reminder of the SPI protocol

As Vlaya already explained, the LED configurations are 16-bits frames (8 address bits and 8 data bits)  send by the main board on a SPI bus. By looking at the firsts bits of the frame, the processor determines whether the following 8 bits configuration concerns it (configuration for one of its LEDs or “TOP” to turn on the LEDs) or not. 

  • If so, it retrieves the following 8 bits on the SPI bus and uses it to configure one of its LEDs or start the flash. 
Read more